1. Field of the Invention
The present invention relates to an automatic soldering apparatus and method for soldering electronic components to a circuit pattern on a circuit board, and more particularly, to an automatic soldering apparatus and method which includes a flux tub with flux therein and a ceramic foaming tube positioned in the flux tub and having compressed air supplied thereto for creating a bubble layer of uniform foaming flux.
2. Description of the Prior Art
In order to carry out a soldering operation upon a circuit board, generally, the leads of electronic components are inserted into holes formed in a circuit pattern on the circuit board, and flux smeared solder is applied and heated and then cooled down to fix the lead of the circuit components to the circuit pattern on the circuit board. However, the soldering operation is a low efficiency operation and workers evade the soldering operation due to the possibility of lead poisoning.
An automatic soldering apparatus developed as an alternate measure is illustrated in FIG. 1. A flux tub 10 is provided to perform a flux treatment upon a circuit board that is passed thereover. A preheating bucket 20 is provided with a heater 22 for drying out and preheating the circuit board that has been subjected to the flux treatment. A soldering tub 26 applies melted solder to the circuit board that has been preheated by the preheating bucket 20, and a cooling tub 30 cools the circuit board after soldering by means of the air flow from a cooling fan 28.
As shown in FIGS. 2 and 3, the flux tub 10 has a trapezoidal chamber 12 therein and a ceramic foaming tube 14 provided in the trapezoidal chamber. The tube 14 has microscopic holes around its circumference and is installed in the lower portion of the flux tub 10. An air supply pipe 16 supplies compressed air to the tube and extends from one side of the ceramic foaming tube 14.
The flux in the flux tub 10 may be any known flux suitable for the soldering application. One known example of the flux is a solvent of 80 wt isopropyl alcohol and 20 wt pine resin. The flux serves in a well known manner to clean that portion of the circuit board to which solder is to be applied in order to facilitate soldering.
Referring back to FIG. 1, the soldering tub 26 has a trapezoidal chamber 32 therein. A laminar flow hovering fan 36, driven by a motor 34, is installed in the lower portion of the soldering tub 26 to push the solder up and over the top of the trapezoidal chamber.
According to the prior art automatic soldering apparatus, when compressed air is forced into the ceramic foaming tube 14 of the flux tub 10 through the compressed air pipe 16, the flux is bubbled and floated as a foaming flux 18 as a result of the action of the compressed air pushing through the holes in the ceramic foaming tube 14, thereby forming a bubble layer. The foaming flux 18 is guided by the chamber 12 to flow outwardly over the edges of the trapezoidal chamber 12 and back into the tub 10. The circuit board to which components are to be soldered, is positioned in the foaming flux and is thereby subjected to a flux treatment.
After being subjected to the flux treatment, the circuit board is transferred to the preheating bucket 20 for the purpose of drying out the foaming flux remaining on the circuit board and preheating the circuit board by the heat generated from the heater 22 within the preheating bucket 20 at a predetermined temperature.
Upon completion of preheating at a predetermined temperature, the circuit board is placed in the laminar flowing solder in chamber 32 of soldering tub 26. The laminar flow hovering fan 36 is rotated below the chamber 32 of the soldering tub 26 by means of the motor 34 to continually cause the solder to flow up and over the edges of the chamber 32. The circuit board contacts the melted lead flowing out of the chamber. The melted lead (solder) solders the leads of the electronic components to the circuit pattern on the circuit board.
When the circuit board that has been fully subjected to the soldering is transferred to the cooling tub 30, the melted lead attached to the pattern of the circuit board and leads of the electronic components are cooled by the air flow generated by the cooling fan 28.
However, in the prior art automatic soldering apparatus, because the compressed air pipe 16 is formed on only one side of the ceramic foaming tube 14 of the flux tub 10, the through holes in the ceramic foaming tube 14 are liable to be locally clogged by foreign substances created within the ceramic foaming tube 14. The clogged through holes vary the pressure within the ceramic foaming tube 14 and, in turn, change dimensions of the foaming flux 18 and the foaming height to surge as waves, so that a circuit board cannot be subjected to a uniform flux treatment.